This simple mod allows you to fly in survival Minecraft. It has three different settings that allow you to have a lot of control over how you fly. When you install the functions, you'll get a book with several settings. Just click on whatever setting you want to activate.

Clear Flight stops you from flying. You will immediately fall to the ground, but you'll have immunity from fall damage for a few seconds.
Flight makes you fly up.
Hover makes you stay in one spot vertical, but you can still move horizontally.
Slowfall makes you slowly fall downward.

This should work in multiplayer, but keep in mind that opening a book in multiplayer doesn't pause the game like it does in singleplayer

Installation 1. Download the zip file 2. Extract or unzip the zip file, there should be a folder named greystalk 3. Got into your .minecraft folder and choose which world you want to install the mod into 4. Go into your world save, data, and then functions 5. Paste in the folder called greystalk 6. Go ingame and run these two commands, /reload /function greystalk:get_book 7. Enjoy!